Hall viscosity: A link between quantum Hall systems, plasmas and liquid crystals

• Connections between simple 2D fluid models in different fields of physics presented.
• Structure emerges via varied physical mechanisms driven by internal angular momentum.
• Properties of these models such as Casimirs, equilibria and stability are analyzed.

In this Letter, the assumption of two simple postulates is shown to give rise to a Hall viscosity term via an action principle formulation. The rationale behind the two postulates is clearly delineated, and the connections to an intrinsic angular momentum are emphasized. By employing this methodology, it is shown that Hall viscosity appears in a wide range of fields, and the interconnectedness of quantum Hall systems, plasmas and nematic liquid crystals is hypothesized. Potential avenues for experimental and theoretical work arising from this cross-fertilization are also indicated.